| Summary: | A tool based on a Techno-economic and Environmental Risk Assessment (TERA)
framework is useful at the preliminary stage of an aero engine design process, to
conceive and assess engines with minimum environmental impact and lowest cost of
ownership, in a variety of emission legislation and taxation policy scenarios.
This research was performed as part of the EU FP6 New Aero engine Core concepts
(NEWAC) programme which was established to assess the potential of innovative gas
turbine core technologies to enhance thermal efficiency thereby reducing CO2
emissions and fuel consumption. A representative prediction of engine life and mission
fuel burn at the earliest possible design stage is a crucial task that can provide an
indication of the approximate overall engine direct operating costs. Two aero engines,
a conventional turbofan and a conceptual intercooled turbofan, were assessed and
optimised using the TERA approach to identify the designs that provided the maximum
time between overhaul (and therefore the minimum maintenance costs). In order to
perform these assessments (which included sensitivity and parametric analyses, and
optimisation studies) several models were developed and integrated in an optimisation
framework. A substantial effort was devoted to the development of a detailed lifing
model that calculates the engine life with a reasonable level of accuracy by integrating
physics based oxidation, creep and fatigue models.
The results obtained from the study demonstrate that an engine optimised for
maximum time between overhaul requires a lower overall pressure ratio and specific
thrust but this comes at the cost of lower thermal efficiency and therefore higher
mission fuel burn.
The main contribution to knowledge of this work is a multidisciplinary TERA
assessment of a novel intercooled conceptual aero engine. Particular emphasis is
placed on the design space exploration and optimisation studies to identify the designs
that may offer the largest time between overhaul. The consequent implications
therefore this may have on mission fuel burn and direct operating costs.
In addition to refining the various TERA models, one of the main recommendations for
further work is to optimise the engines for minimum direct operating cost to identify the
best economic compromise between engine life and mission fuel burn. This can be
done by considering different fuel prices and under a variety of hypothetical emission
taxation scenarios, to identify the circumstances in which intercooled engine
technology may become economically viable.
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